Telephone-exchange system



Jan, '20. 1925.

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Patented Jan. 20, 1925.

LIPA POLINKOWSKY, F AN'IWERP, BELGIUM, ASSIGNOB TO COIVIIANY, INCORPORATED, OF NEW YORK,

"WESTERN ELECTRIC N. Y., A CORPORATION OF NEW YORK.

TELEPHC'NE-EXCHANGE SYSTEM.

Application filed April 29, 1920.

T0 (zZZ 20710222 it may concern.

Be it known that I, LIPA Ponimiowsnir, a

citizen of Russia, residing at Antwerp, Belgium, have invented certain new and useful ln'iprovei'nents in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems in which machine switching apparatus is utilized for establishing connections between subscribers lines.

More particularly, the invention relates to a telephone system involving a plurality o1 switching stations or exchanges provided with interconnecting trunk lines, whereb subscribers whose lines terminate in one switching station may obtain connections with other lines local thereto, or by means of said interconnecting trunks may extend a connection to a distant exchange or switching station and thence to a desired line therein.

The object of the invention is the provision in a system of this character where the designation of a called line is registered on a controlling mechanism to control the auto matic switches, of means whereby it the desiredline is in a distant exchange, the controlling mechanism at the originating exchange is set only'in accordance with the of the originating exchange, such controlling mechanism operates to cause the final selector ot' the originating exchange to function as a group selector to select an idle trunk outgoing to the distant exchange in which the desired line terminates.

Another feature of the invention resides in the provision of switching means asso ciated with the switch controlling mechanism for connecting the registering elements of the mechanism successively to the line oi Serial No. 377,709.

the calling subscriber and then successively to the fundamental switch controlling circuit, and for connecting the controlling mechanism in succession with the ditl'erent finder link circuits which it. is arranged to serve.

These and other features of the invention will become more apparent as the description progresses. Reference will now be made to the accompanying drawings in which Fig. 1 shows a subscriber-"s line terminating in the multiple contacts of first line finder switches in a branch exchange or satellite, and the operating circuits of one of these finder switches;

Fig. 2 shows one of a plurality of secondary line finder switches in the satellite. in. the multiple terminals of which appear the connecting circuits leading from the first line finder switches. There is also shown a final selector switch of the satellite paired with the secondary finder switch, together with the necessary circuits and apparatus for operating these switches;

Fig. 3 shows a switch controlling register mechanism for controlling the selector switches at the satellite, together with the operating circuits therefor, and means for associating the mechanism with an idle finder link circuit;

' Fig. 4 shows the incoming end of a trunk. line leading from the terminal bank of the final selector of the satellite to a distant exchange, and the circuits of a first line finder of a group at the distant exchange having access to the terminals of the trunk line and to subscribers l .es icon to the distant crachange;

Fig. 5 shows one 01" a group of secondary line finder switches in the distant exchange in the multiple terminals of which appear the connecting circuits leading from the first finder switches and a final selector switch linked to the secondary line tinder, together with the necessary circuits and apparatus for operating these switches; and

Fig. 6 shows a switch controlling register mechanism for controlling the selector switches at the distant exchange, together with the operating circuits therefor, and means for associating the mechanism with an idle finder link circuit.

In order to illustrate the organization of this system for enabling a connection to be established between a subscribers line in a ion lit)

satellite, and a subscribers line in the distant exchange, Figs. 1, 2, 4 and 5 should be placed end to end in the order set forth. Fig. 3 should be placed beneath Fig. 2, and Fig. 6 should be placed beneath Fig. 5.

In .the system disclosed, where satellite and distant exchanges are involved with trunking facilities whereby a subscriber in the satellite is enabled to obtain telephone connections with subscribers lines belonging to the distant exchange, provision is also made at the satellite such that a subscriber therein may obtain connections directly to the lines of other subscribers local to his satellite without first extending the connection over the trunk to the exchange or utilizing any of the exchange apparatus. The satellite of this system represented by the circuits and apparatus shown in Figs. 1, 2 and 3 may be of any suitable capacity but for the purpose of illustrationis shown as having a capacity of 200 lines whereby only 2 selective operations are required for completing a connection between two lines local to the satellite. Since, however, the subscribers of the satellite may have access to trunks leading to a distant exchange, it is further necessary to selectively determine whether the call is to be local to the satellite or to be extended to the distant exchange. The switch controlling mechanism at the satellite is therefore arranged to register three digits, the first digit for determining the office designation of the desired line, and the remaining digits for determining the line in the selected oliice.

To accomplish the foregoing purpose, the register controlling mechanism at the satellite is provided with two registers, the first register being adapted to be first set in accordance with the otiiee designation of the desired line, and then in accordance with the tens digit of the line, and the second register being set-in accordance with the units digit. The register mechanism shown in the present system is of the type in which sequence switches are provided for the registration of the digits. Each sequence switch has ten positions and advances to a position corresponding to the number of impulses sent from the subscribers dial during the setting period of the registers, and later runs through the remaining positions of its cycle to control the operation of the selector switches. It is therefore obvious that the number of steps taken by a register while controlling a selector switch is the complement of the number of impulses sent by the calling subscriber. In order that the switches may be controlled in accordancewith numerical designations of the called numbers, it only becomes necessary to ar range the calling subscribers dial so that the complement rather than the actual digit itself be sent to the register. The subscribers dial is further designed so that the last lnterruption of the line in each ser1es of nnpulses 1s of comparatively longer duration than the interruptions of the preced ing impulses of the series. The register controlling mechanism at the distant exchange is of substantially the same construction as the controlling mechanism at the satellite.

For successively associating the registers of the controlling mechanism with the sub scribers line in order that they may be set in accordance with the designation of the desired line, a switch of the sequence switch type is provided, which in certain positions also connects the registers with the fundamental circuit extending to the selector switches. This sequence switch has eighteen positions and performs its various connecting functions three times per revolution. In addition to the functions of associating the registers with the calling line and with the fundamental circuit, it also serves as a preselector switch for preselecting a secondary finder link for use in associating the circuits of the register controlling mechanism with the selected link.

It is believed that a more thorough understanding of the invention may be had from a description of the mode of operation of the system in extending a call from one sub scribers line to another. First it will. be assumed that a subscriber at substation A in the satellite desires to obtain a connection with another line B, local to his, own satellite.

Easlenslon of a local call in the satellite.

On removing his receiver from the switchhook to initiate a call, a circuitis established from battery through the winding of line relay 201, contact and left-hand armature of cut-off relay 207 over the loop of the calling line and returning by way of the right-hand armature and back contact of relay 207 to ground. Relay 201 attracting its armatures closes a circuit from battery through resistance element 202, armature and front contact of relay 201 to place a selectable potential upon the multiple terminals 210 of the calling line appearing in the banks of all first line finder switches having access to the group in which the calling line appears.

At its left-hand armature and front contact, relay 201 closes a starting circuit extending in parallel through the windings of the power magnets 211, back contacts and armatures of relays 212, and back contacts and armatures of relays 213 to a grounded battery, of all idle first line finder switches. These switches thereuponrotate their brush carriages in the well known manner to advance their brushes over the multiple terminals of their banks in search of the calling line. As soon as a finder switch moves its test brush into engagement with the test terminal 210 of the calling line, the selectable potential is found thereon and a circuit is closed through the test brush through the left-hand high resistance winding of test relay 214 to ground. Relay 214 attracts its armature and closes a circuit through its right-hand low resistance winding and the winding of the second test relay 212. This circuit being in shunt of the left-hand winding of relay 214 reduces the potential on multiple terminals 210 to render the calling line non-selectable. Relay 212 energizes when the brushes are accurately centered on the terminals of the calling line and opens the power circuit extending through the power magnet 211, thereby bringing the brush carriage to rest. A circuit is now completed from grounded battery through the armature and back contact of relay 213, armature and front contact of relay 212 to place selectable potential upon the multiple terminals 230 appearing in the terminal banks of all second line finder switches having access to the connecting circuit of the first line finder switch which has selected the calling line. For the purpose of this discussion, it will be assumed that the second finder switch shown in Fig. 2 is the finder which ultimately searches for and makes connection with the first finder connecting circuit. In parallel with the circuit extending to the test terminal 230, a circuit is established through the winding of holding magnet 215 and through the wind ngs of the common starting relays 216 to ground. Relays 216 energize and establish a starting circuit for the second finder switch, assuming that the second finder switch shown in Fig. 2 has been preselected for use by the register controlling mechanism, which may be traced from grounded battery through the starting relay 222, lower contact of sequence switch spring 223 (1), conductor 393, upper contact of sequence switch spring 322 (1), the normally closed left-hand armature contacts 01" relay 341, the upper contact of sequence switch spring 323 (l), conductor 395 and thence to ground at the front contacts and armatures of relays 216. Relay 222 energizes in this circuit and at its armature and front contact closes a circuit for power magnet 241 of the second finder switch, which circuit may be traced from grounded battery through the magnet winding 241, upper contact of sequence switch spring 224 (1), back contact and armatureot relay 232, and thence to ground through the armature and front contact of relay 222. The power magnet causes the brush carriage of the second line finder switch to rotate in the well known manner until the brushes of the switch engage the multiple terminals of the connecting circuit of the first finder switch which has been taken for use, when selectable potential is encountered at the test terminal 230, and a circuit is established for the test relay 234 which may be traced from grounded battery through the armature and back contact of relay 213, the armature and front contact of relay 212, resistance 217, terminal 230, lower contact 0t sequence switch spring 226 (1 to 3), righthand high resistance winding of relay 234, upper contact of sequence switch spring 225 (1), and thence to ground through the right-hand armature and back contact of relay 263. Relay 234 upon energizing connects its low resistance left-hand winding and the winding of relay 282 in parallel with its lefthand high resistance winding for the purpose of reducing the potential upon the test terminal 230 to replace the calling potential upon such test terminal with a noncalling potential. Relay 32 upon energizing closes a circuit for driving sequence 220 out of position 1 and under the control of the master contact 221 into position 3. This circuit may be traced from grounded battery through the magnet winding of sequence switch 220 through. the lower contact of sequence switch spring 227 (1), the front contact and armature of relay 232, and thence to ground at the front contact and armature of relay 222. A circuit is also closed at this time in parallel with the magnet windingof the sequence switch through the lower contact of sequence switch spring 228 (1 and 2), through the winding of the holding magnet 245 and thence to battery. The magnet 245 thereupon arrests the brushes of the finder switch in contact with the terminals leading to the first finder switch.

Upon leaving position 1, sequence switch 220 opens the circuit of the power magnet 241 at the upper contact of sequence switch. spring 224, and in passing through position 2 establishes a new circuit for the relay whichmay be traced from; grounded bah tery through the winding of this relay through the upper contact of sequence switch spring 223 (2), through the back contact and armature of relay 262, through the lower contact of sequence switch spring 238 (2) and thence to ground through the lower contact of sequence switch spring 229 (1 and 2). Upon reaching position 3, a circuit is established for the relay which may be traced from grounded battery through the right-hand winding of this relay, through the lower contact of sequence switch spring 236 (3), and thence to ground through the normal contact 269 of the brush carriage of the final selector switch. In passing position 2 a circuit is established for the line relay 325 of the register controlling mechanism, which may be traced from grounded battery through the right-hand winding of relay 325, conductor 392, upper contact of sequence switch spring 237 (2 to 6), the left-hand normally closed armature contacts of relay 233, conductor 390, upper contact of sequence switch spring 320 (1 and 1 and thence to ground through resistance element 327. This circuit is established for the purpose of preventing a premature release in the event that the brushes of the second finder switch, upon engaging the terminals leading through the brushes of the first finder switch to the calling line, find the line open. In position 3 sequence switch 220 establishes a circuit for the cutoff relay 207 of the calling line, relay 213 of the first finder switch and relay 233 of the second finder switch, which may be traced from grounded battery through the winding of relay 207, through bank terminal 218 of the first finder switch, winding of relay 213, bank terminal 233 of the second finder switch, winding of relay 233, back contact and left-hand armature of relay 203, and thence to ground through the upper contact of sequence switch spring 229 (3 to 7). These relays energize in this circuit.

Relay 207 upon energizing disconnects the winding of line relay 201 from the limbs of the calling line. The line relay 201 thereupon deenergizes opening at its lefthand armature contact, the circuits extending through the power magnets 211 of all idle first finder switches, thereby bringing the brush carriages of these switches to rest. At its right-hand armature, relay 201 removes calling potential from the test ter- --minal 210, thereby causing the deenergization of relays 214 and 212, thereby restoring the circuits of the first finder switch to nornial condition. Relay 213 upon energizing opens the circuit extending through relays 216, which in turn deenergize and open the initial starting circuit over conductor 395. Relay 213 also removes calling potential from the terminal 230, thereby causing the deenergization of test relays 234 and 232. Relay 233 upon energization connects the calling line through to sequence switch contacts 235 and 237 and, since these contacts are now closed, the line is further extended over conductors 391 and 392 through the windings of relay 325.

Relay 325 attracts its armature thereby establishing a circuit for the magnet winding of register switch 130, which may be traced from grounded battery through the magnet winding, through the lower contact of sequence switch spring 332 (1 and 2), through right-hand armature and back contact of relay 331, the back contact and armature and left-hand winding of relay 329, lower contact of sequence switch spring 328 (1 to 3), back contact and armature of relay 357 and thence to ground at the front contact and armature of relay 325. The register switch thereupon moves out of its normal position and while passing into position 1 closes a shunt around the lefthand winding of relay 329 at switch spring 131. of a circuit extending through its low re sistance, right-hand winding through the resistance element 333 to grounded battery, this winding being wound differentially to the left-hand winding of the relay. Relay 329 upon energizing opens at its armature and back contact the initial circuit of reg ister switch 130, switch 130 being driven into position 1 over contact 131. A circuit is also established for relay 341, which extends from grounded battery through the winding of this relay, its normally closed right-hand armature contacts, the lower contacts of the sequence switch spring 334 (1), and thence toground at the front con tact and armature of relay 325. upon energizing opens its initial energizing circuit and locks itself up through its right-hand armature contacts, through the left-hand winding of relay 342 and the upper. contact of sequence switch spring 335 (1). Relay 342 upon energizing prepares a circuit for the slow to energize relay 343, which extends through the armature and front contact of relay 342, the lower contact of sequence switch spring 336 (1), and through the back contact of relay 325, which circuit is-effective upon a subsequent deenergization of the relay 325. Relay 343 has been illustrated as slow to energize by the weighted arrow applied to its armature, the arrow indicating that the relay upon energization must overcome inertia, acting to retard the movement of the armature in the direction indicated by the arrow. The inertia is represented by the small ball on the outer end of the arrow.

lVhen register switch 130 moves into position 1, a circuit is closed from grounded Relay 329 now energizes by virtue.

Relay 341 battery through the primary winding of the tone coil 324, the upper contact of seruiencc switch spring 337 (1), register switch con tact (1) and through the interrupter 338 to ground. A tone current is thereupon transmitted to the line of the calling subscriber, and the subscriber upon hearingthe tone is apprised of the fact that/he may 1 begin to dial the number of the desired line; Setting the register controlling mechtmsm.

lfll) hundreds group, and since the dial is so arranged as to send the complement of the digit rather than the digit itself, the dial will interrupt a circuit through the relay 325 either eight or nine times. Each time the circuit is interrupted through the relay 325, tl e circuit previously traced through the relay 329 is interrupted, and the relay upon retracting its arn'iature closes a circuit for the register switch 130 and, as previously described, the sequence switch 130'in moving from one position into its next succeeding position closes at contact 131 a shunt around the left-hand winding of relay 329 whereby this relay is permitted to re-energize upon the re-establishment of this circuit at the front contact and armature of relay 329, following each deenergization of relay 325. The register switch 130 is thereby advanced to either position 8 or 9. Upon the last comparatively long deenergization of relay 325, a circuit is established through the slow to energize relay 343 which thereupon energizes and at its armature and front contact closes a circuit for driving the sequence switch 320 into position 2. Upon leaving position 1, the circuit previously traced through relays 34.1 and 342 is opened and these relays retract their -armatures. Relay 343 is now connected over the armature and back con tact of relay 342, through the upper contact of sequence switch spring 339 (2) and thence to the back contact of relay 325, but relay 343 does not energize at this time since, following the last impulse of the first series, relay 325 re-energized, If the register 130 when operating in the circuit described was arrested in position 8, a circuit was established momentarily while the sequence switch 320 is passing from position 1 into position 2 which may be traced from grounded battery through the windings of relays 374 and 373, register contact 136 (8) and thence to ground at the lower contact of sequence switch spring 344 (1 These relays immediately lock up over a circuit extending through the front contact and armature of relay 373 and thence to ground at the lower contact of sequence switch spring 323 (2 and 3). The register 130 is now restored to its 0 or normal position by a circuit which was closed in parallel with the circuit through the magnet winding of sequence switch 320 at the time relay 343' energized. This circuit may be traced from grounded battery through the righthand winding of relay 357 through the winding of relay 331, lower contact of sequence switch spring 345 (1), and thence to ground at the front contact and armature of relay Relays 331 and 357 energize in this circuit and are locked up over a local circuit extending through their windings and to ground through the front contact and: left-hand armature of relay 331. At its right-hand armature and front con tact, with the sequence switch 320 now in position 2, a circuit is closed through the magnet winding of the register 130, through the lower contact of sequence switch spring (1 and 2), through the right-hand armature and front contact of relay 331, contact 137 (1 to 9) of register 130, lower contact of sequence switch spring 322 (2), normally closed left-hand armature contacts of relay 341 and thence to ground at the lower contact of sequence switch spring 323 (2 and 3). Register 130 now proceeds to move around until it reaches its normal position when a shunt circuit is closed around the winding of relay 331 at the register con tact 133, the relay 331 thereupon deenergizing and opening the circuit of the register magnet 130. Relay"331 also open at its :-;5

left-hand armature and front contact the locking circuit extending through the righthand winding of relay 357, which now ceenergizes. A circuit is now closed extending from the armature contacts of relay and through relay 329 for driving register 130 into position 1. Relay 329, however, does not energize in the circuit traced since at this time a circuit also extends through its right-hand winding and resistance 333 to grounded battery. lVhen, however, the register 130 rotates from normal into position 1, the left-hand winding of relay 329 is shunted at the register contact 131 and the relay 329 thereupon energizes opening at its armature contact the initial circuit of the register magnet 130, the register being driven into position 1 over contact 131.

In response to the second series of impulses, relay 325, in the manner previously described, causes the register 130 to move into a position corresponding to the digit of the second series dialed by the calling subscriber. In response to the last opening of the line, relay 325 retracts its armature for a sufiicient time to permit the slow to energize relay 343 to energize over the circuit previously traced, thereby causing sequence switch 320 to move out of position 2 and into position 3. A circuit is also closed in parallel with the winding of sequence switch magnet 320, which extends through the upper contact of sequence switch spring 345 (2 and 3), through the left-hand winding of relay 357 to grounded battery. hen sequence switch 320 reaches position 3, relay 357 deenergizes thereby closing a cir cuit for the magnet winding of the register 140, which circuit may be traced from grounded battery through this magnet winding, through the upper contact of sequence switch spring 347 (3), through the back contact and right-hand armature of re lay 331, the back contact and armature and left-hand winding of relay 329, contact of Lil sequence switch spring 328 (1 to 3) back contact and armature of relay 357 and thence to ground through the armature and front contact of relay 325, since at this time the relay 325 is energized, the dial having returned to normal, following the second series of impulses. Register 140 starts up and moves into position 1, the register contact 141 establishing a shunt around the left-hand winding of relay 329 during its movement. Relay 329 thereupon energizes in the manner previously described opening at its armature contacts the initial energizing circuit for the register magnet 140, whereby the register is brought to rest in position 1. Sequence switch 320 upon moving into position 3 also closes a circuit for relay341, which may be traced from grounded battery through the winding of this relay and thence to ground through the upper contact of sequence switch spring 344 (3), and the relay 341 upon energization closes a circuit extending from battery through the righthand winding of relay 342, left-hand armature and front contact 01 relay 341 and thence to ground at the lower contact of sequence switch spring 323 (2 and 3). Relay 342 attracts its armature and prepares a circuit for the slow to energize relay 343 extending through the lower contact of se' quence switch spring 336 (3), which becomes etlective upon the last deenergization oi" the relay 325 following the third series of impulses. The circuits of the register are now in condition for receiving the third series of impulses.

The third series of impulses causes the operation of the line relay 325 in the manner previously described for causing the register 140 to be advanced to a position corresponding to the digit dialed by the calling subscriber, and upon completion of the series of impulses, the relay 3.15 causes the energization of relay 343 for driving the sequence switch 320 out of position 3 and into position 5. Upon leaving position 3 the circuit of relay 341 is opened at sequence switch contact 344 andthis relay retracts it's armatures, thereby opening the circuit of relay 342. Relay 342 at its armature and back contact now prepares a circuit for the slow to energize relay 343 which is later effective through the lower contact of sequence switch 339 (5).

Operation of the final selector switch.

)Vith the sequence switch 220 in position 3 and sequence switch 320 in position 5, a fundamental circuit is established extending from the register controlling mechanism to the final selector switch, which may be traced from grounded battery through the winding of relay 222, lower contact of sequence switch spring 223 (3 to 6), conductor 393, upper contact of sequence switch spring 356 (1 to 6), winding of stepping relay 355, upper contact of sequence switch spring 346 (5 and'6) through the back contact and armature of relay 357 and thence to ground through the upper contact of sequence swltch spring 334 (5 and 6). At the front contact the armature of relay 222, a circuit is established for the trip spindle magnet 248 of the final selector to ground through the front contact and.

armature of relay 22-2. The trip spindle now rotates and, at the upper trip spindle I contacts 255, intermittently connects a, shunt circuit around the winding 0]": stepping relay 355 of the register controlling mechanism,

which circuit may be traced from ground,

through the upper contacts 255, the upper left-hand contacts of sequence switch spring 249 (3 to G) and thence to the junction point at sequence switch spring 223 between wind ings of the relay 222 and the stepping relay 355. Relay 222 maintains its energization, but relay 355 deenergizes upon each closure of the shunt circuit. As soon as the trip spindle moves out of its normal position,a circuit is established at the lower trip spindle contact 255 for driving the sequence switch 220 out of position 3 and into position 4, this circuit extending from grounded battery through the magnet winding 220, through the lower contact of sequence switch spring 227 (3), through the front contact and armature of relay 262 and thence to ground at the contact 255., Upon each deenergization of relay 355, a circuit-is established for the register magnet 130, which may be traced from grounded battery through the winding of the magnet of the register, contact 132, the upper contact of sequence switch spring 332 (5), right-hand armature and back contact of relay 331.; back contact and armature and left-hand winding of relay 329, upper contact of sequence switch spring 328 (5), and thence to ground at the back contact and armature of relay 355. A circuit is also closed at this time in parallelwith the left-hand winding of relay 329 through the low resistance right hand winding of this relay,'through the resistance 333, and thence to battery. Relay 329 does not energize at this time, however, since its windings are difierentially wound. As soon, however, as the register 130 starts to move into its next succeeding position, contact 131 establishes a shunt around the left-hand winding of relay 329 and this relay. energizes, opening the initial circuit of the register mag net 130, the register being driven into its next stopping position by spring 131. Thus upon each dee ner-gization of relay 355, register 130 is caused tomove from one position into the next succeeding position and until it has advanced to its normal position, when a circuitis established for the relay 357, which may be traced from grounded battery through the left-hand winding of this relay, through the register contact 134., the upper contact of sequence switch spring 332 (5), the armature and back contact of relay 331, the back contact and arn'iature and left-hand winding of relay 329, the upper contact of sequence switch spring 328 (5) and thence to ground at the back contact and armature of relay Relay energizes in this circuit and at its armature and back contact opens the fundamental circuit extending through the relays 355 and 222, and relay 222 thereupon deenergizes. Relay 222 upon deenergizing opens the driving circuit extending through the trip spindle magnet 248', thereby arresting the movement of the trip spindle and, at its armature and back contact, closes a circuit extending over the upper contact of sequence switch spring251 l) for driving the sequence switch 220- out of position 4:, and under the control of the master contact 221, into position 6.

Upon the energization of relay 357, a circuit is closed through its armature and front contact for the slow to energize relay which circuit may be traced from grounded battery through the winding of this relay, through the armature and back contact of relay 342, the lower contact of sequence switch spring 339 (5), the front contact and armature of relay 357 and thence to ground at the upper contact of sequence switch spring 334 Relay 3&3 energizes in this circuit and at its armature and front contact establishes a circuit for driving sequence switch 320 out of position 5 and into position 6. As soon as sequence switch leaves position relay 357 deenergizes and the fundamental circuit through the relays 2 22 and 355 is again closed through its arn'iature and back contact. Relay 222 upon energizing closes a circuit for the brush carriage driving magnet 261, which may be traced from grounded battery through the winding of this magnet, the lower contact of sequence switch spring 22- (6), the back contacts and armature of relay 232, and thence to ground through the front contact and armature of relay The magnet 2G1 thereupon rotates the switch shaft carrying the brush sets past the tripping spindle and, in accordance with the setting of the tripping spindle, causes one of the brush sets to be tripped. Gontinued notation of the brush carriage moves the tripped set of brushes over the row of terminals corresponding thereto. During the rotation of the brush carriage, the

cam springs 251 cause the periodical connection of a shunt circuit around the winding of the stepping relay 355 of the register controlling mechanism, thereby causing the relay 355 to be intermittently deenergized. The relay 222 is, however, maintained energized over the shunt circuit, which may be traced from the winding of relay 222 through the upper left-hand contact of sequence switch spring 24-9 (3 to 6) and thence to ground through the upper cam springs 251. Upon each deenergization of relay 355, a circuit is established for the register magnet 140 extending from grounded battery through the magnet winding of the register, contact 142, sequence switch spring 347 (6), armature and back contact of relay 331, the back contact and armature and left-hand winding of relay 329, the upper contact of sequence switch spring 328 (6) and thence to ground through the back contact and armature of relay 355. In the manner hereinbeforeexplained, the register 140 is driven step-by-step into its normal position when a circuit is established for the relay 357, which may be traced from grounded battery through the left-hand winding of this relay, contact 13 i of register 130 (0), contact 144 (0) of register 140, the back contactand armature of relay 374i, register contact 143 O) ,the lower contact of sequence switch spring 3 17 (6) and thence over the circuit previously traced to ground at the back contact and armature of relay 355. Relay 357 energizes in this circuit opening at its armature and back contact the fundamcn ta circuit extending through relays 355 and 222, and at its armature and front contact establishing a circuit extending from ground at the upper contact of sequence switch spring 334 (6), through the armature and front contact of relay 357, the upper con tact of sequence switch spring 358 (6). and thence through the magnet winding of sequence switch 320 to grounded battery for driving the sequence switch out of position 6 and into position 7 The register controlling mechanism is now in normal condition and with the sequence switch in position 7 is associated with the next idle second finder link circuit.

If at this time the next idle link circuit is busy, sequence switch 320 will not re main in position 7 but will be driven through its successive positions into position 13. As suming that the next link circuit is busy. the sequence switch 220 of such busy link circuit will be standing in some position between 7 and 16 and a circuit will therefore be established from ground at the lower contact of sequence switch spring 229 of an idle link of the group in positions 1 and 2 or 17 and 18, over conductor 397, through the upper contact of sequence switch spring 238 (7 to 16) of the busy link circuit, over ill) conductor 398, Fig. 2, the continuation of conductor 398, Fig. 3, through the lower contact of sequence switch spring 359 (7 to 9) and thence through the winding of the magnet of sequence switch 320. The sequence switch therefore rotates from position 7 through position 9 and into position 11. Upon reaching position 11, a circuit is established for relay 357, which may be traced from grounded battery, through the left-hand winding of this relay, register contact 134 (0), upper contact of sequence switch spring 332 (11), and thence through the contact of relays 331 and 329, through the upper contact of sequence switch spring 328 (11) to ground at the back contact and armature of relay 355. Relay 357 energizes in this circuit and at its armature and front contact closes a circuit for the relay 343, which may be traced through the winding of this relay, through the armature and back contact of relay 342, the lower contact of sequence switch spring 339 (11), the front contact and armature of relay 357, and thence to ground through the upper contact of sequence switch spring 334 (11 and 12). Relay 343 attracts its armature, thereby establishing a circuit for sequence switch 320 which is then driven out of position 11 and into position 12. Upon leaving position 11, relay 357 deenergizes, but in position 12 01": the sequence switch this relay reenergizes over a circuit traced through register contact 134 (0), through register contact 144 (0), the back contact and armature of relay 374, register contact 143, the lower contact of sequence switch spring 347 (12), and thence to ground over the circuit previously traced, at the back contact and armature of relay 355. Relay 357 upon energizing in this circuit establishcs a circuit for driving sequence switch 320 out of position 12 and into position 13, this circuit extending from the winding of the sequence switch magnet 320 through the upper contact of sequence switch spring 353 (12), the front contact and armature of relay 557 and thence to ground through the upper contact of sequence switch spring 334 (11 and 12). It upon reaching position .13, the link with which the register controlling mechanism is then associated is busy, the register will, in a similar manner, be driven out of position 13 and into position 1.

Upon the opening of the fundamental circuit, after the positioning of the brush carriage in accordance with the setting of register 140, relay 222 deenergizes opening at its armature and front contact, the circuit of the brush carriage magnet 261, and closes at its armature and back contact a circuit for the holding magnet 265 which circuit may be traced from grounded battery through this magnet winding, through the upper contact of sequence switch spring 228 (6), the upper contact of sequence switch spring 251 (6) and thence to ground at the back contact and armature of relay 222. A circuit is also closed in parallel with the magnet 265,.thro-ugh the magnet of sequence switch, 220 for driving the sequence switch.

out of position 6, and under the control of the master contact 221, into position SJ If the register 130 had been set in position 8, and relays 373 and 374 had been energized, then when the register 140 reached its normal position, it would have continued in rotation, since with relay 374 energized, the circuit of the magnet 140 is continued through the lower contact of sequence switch spring 347 (6), the register contact 143 (0), the armature and front contact of relay 37 4, and thence through the winding of the register magnet 140to battery. As soon, however, as the register leaves its normal position and before it reaches position 1, the circuit which has been holding relays 373 and 374 energized, which extends through the windings of these relays, through the armature and front contact of relay 373, through register contact 146 (0),

and thence to ground at the lower contact of sequence switch spring 335 (3 to 6) is opened at register contact 146. The funda mental circuit is maintained when the register reaches position 0, since at that time relay 374 was energized and no circuit was effective for the relay 357. The register 140 now continues to rotate until it reaches its 0 position a second time when the relay 357 Testing the called line, the line being idle.

Sequence switch 220 upon the deener'gization of relay 222 moved out of position 6 and into position 8. )Vhen leaving position 6,

the circuit extending through the relay 325' of the register control-ling mechanism is opened at the sequence switch springs 235 and 237, and in position 7 the calling line is extended over the upper contact of sequence switch spring 235 and over the lower contact of sequence switch spring 237 to the windings of the ansii'ering supervisory relay 231, which energizes and at its armature and front contact establishes a new holding circuit through the relays 207. 213 and 233. In passing through position 7, a circuit is temporarily established for the testing relay 234, which circuitmay be traced from grounded battery through the winding of cut-ofl relay 284 of the called line,-over test terminal 285, through the uper contact of sequence switch spring 226 (7 to 1.2),through the right-liar] d winding of test relay234, the upper contact of sequence switch spring 225 tit) (7), and thence to ground through the right hand armature and back contact of relay 263. If the called line is idle, as assumed, relay 23% energizes in this circuit and at its armature and front contact closes a locking circuit for itself extending through its lefthand low resistance winding and through the winding of relay 232. This locking circuit also places busy potential upon the test terminal. of the called line to prevent seizure of the called line by other final selector switches. Sequence 220 upon reaching position 8 closes a circuit for relay 222, which may be traced from grounded battery through the winding of this relay, through the upper contact of sequence switch spring 223 (3 and 9), the back contact and armature of relay 262, and thence to ground at the lower cam sprin 255 of the tripping spindle. Relay 222 energizes in this circuit and at its armature and front contact closes a circuit extending through the armature and front contact of relay 232, the lower contact of sequence switch spring 227 (8 to 10), and thence through the winding of the sequence switch magnet 220 to grounded battery, and the sequence.- switch therefor does not stop in position 8 but continues through position 9 and into position 10. Upon reaching position 10, the circuit of relay 222 is opened at sequence switch spring 223 and this relay deenergizes.

In position 10 a circuit is established for the application of ringing current to the line of the called subscriber which circuit may be traced from a source of ringing current 285 through the lower contact of sequence switch spring 266 (10) thence over the called subscribers line and back through the upper contact of sequence switch spring 264 (10) and through the winding of the ringing cut-oil relay 260 to grounded battery. Upon the response of the called subscriber, relay 260 energizes and at its arn'iature and front contact closes a circuit extending through the lower contact of sequence switch spring 227 (8 to 10) for driving sequence switch 220 out of-position 10 and into position 11. During the application of ringing current, while the sequence switch is in position 10, a ringing tone is transmitted to the line of the calling subscriber by means of a ringing tone interrupter 273 which is connected through the lower contact of sequence switch spring 243 (10) and through the primary winding of the tone coil 272, the secondary winding of the tone coil being connected through the windings of relay 262 and through the connections extending back to the line of the calling subscriber. A talking connection is now extended from the line of the calling subscriber to the line of the called subscriber through the upper contact of sequence switch spring the lower contact of sequence switch spring 267 (11 and 12), the upper contact of sequence switch spring 236 (11 and 12) and the lower contact of sequence switch spring 237, talking current being supplied to the calling subscribcrs line through the windings of relay 231, and talking current being supplied to the line of the called subscriber through the windings of relay 262.

Hrstoretio-necalling subscriber first to hang up.

It the calling subscriber is the first to restore his receiver to its switchho'ok, the circuit through relay 231 is opened and this relay deenergizes, opening at its armature and front contact the circuit which has held relays 207, 213 and 233 energized. Relay 207 thereupon deenergizes and at its armature and back contacts reconnects the line relay 201 to the limbs of the calling subscribers line. Relay 213 restores the circuits of the primary line finder to normal condition, and relay 233 disconnects the brushes of the second finder switch from the second finder link. At its armature and back contact, relay 231 closes a circuit for driving sequence switch 220 out of position 11 and into position 12, this circuit being traced from grounded battery through the winding of the sequence switch magnet, through the lower contact of sequence switch spring 251 (10 and 11), through the low resistance right-hand winding of relay 263, and thence to ground through the back contact and armature of relay 231. Upon reaching position 12, sequence switch 220 awaits the restoration of the called subscribers rc ceiver to its switchhook. When this takes place, relay 262 deenergizes, thereby closing a circuit for the relay 222 which may be traced from grounded battery through the winding of this relay through the upper con tact of sequence switch spring 223 (11 and 12), the back contact and armature of relay 262 and thence to ground at the lower contacts of cam Relay 222 energizes, est: 1;- lishing a circuit for driving sequence switch 220 out of position 12 and into position 13, this circuit being traced from grounded battery through the magnet winding of sequence switch 220, the upper contact of sequence switch spring 227 (11 and 12), and thence to ground through the front con tact and armature of relay 222. When sequence switch 220 leaves position 12, the circuit of relay 222 is opened at the upper contact of sequence switch spring 223. In position 13, a circuit is again established through the right-hand winding of relay and through the lower contact of soquence switch spring 251 (13 and 1 1) for driving sequence switch 220 out of position 13 through position 1 1 and into position 15. i circuit is now established for Telback cont-act and armature of relay 268.

Relay 260 energizes, and at its armature and front contact closes a circuit extending through the lower contact of sequence switch spring 227 (13 and 15) for driving sequence switch 220 out of position 15 and into position 16. A circuit is now established for reenergizing relay 222, which circuit may be traced from grounded battery through the winding of this relay, the upper contact of sequence switch spring 223 (16 and 17), the back contact and armature of relay 262 and thence to ground at the lower contact of cam 255; At its armature and front contact, relay 222 establishes a circuit for the trip spindle magnet 2 18 which may be traced from grounded battery through the winding of this magnet, the right contact of sequence switch spring 247 (16), through the hack contact and armature of relay 232 and thence to ground at the front contact and armature of relay 222. The magnet 2&8 rotates the trip spindle around into normal position when the cam 255 opens the circuit previously traced for relay 222, which thereupon deenergizes opening the circuit of the trip spindle magnet 248 causing the Cal trip spindle to come to rest. At its armature and back contact, relay 222 now closes a circuit extending through the upper contact of sequence switch spring 251 for driving the sequence switch out of position 16 and into position 17.

In position 17 a circuit is established for energizing relay 222, which circuit extends from grounded battery through the winding of this relay, the upper contact of sequence switch spring 223 (16 and 17 the back contact and armature oi relay 262, the lower contact of sequence switch spring 238 (17), and thence to ground at the lower contact of sequence switch spring 229 (17). Relay 222 upon energizing closes at its armature and front contact a circuit for the brush carriage driving magnet 261, which extends from grounded battery through the winding of this magnet, the lower contact of sequence switch spring 224 (17), the back contact and armature of relay 232 and thence to ground at the front contact and armature of relay 222. Under the influence of the magnet 261, the brush carriage is rotated around into normal position. Upon reaching its normal position, the normal contact 269 is closed, thereby establishing a circuit extending therefrom through the lower contact of sequence switch spring 236 (17 and thence through the right-hand winding of relay 262 to grounded battery. Relay 262 enerizes in this circuit opening at its armature and back contact the circuit of relay 222,

which immediately deenergizes opening at its armature and front contact the circuit extending through the driving magnet'261, and closing at its armature and back contact a circuit extending from grounded battery through the winding of the holding magnet 265, the upper contact of sequence switch spring 228 (17 the upper contact of sequence switchspring 251 (16 and 17) and thence to ground through the back contact and armature of relay 222. The energ'ization of holding magnet 265 arreststhe brush carriage in its normal position. The

deenergization of relay 222 also establishes a circuit extending in parallel with the winding of magnet 265, for driving sequence switch 222 out of position 17 and into position 18. In leaving position 17, the circuit through the right-hand winding of relay 262 is opened at sequence switch contact 236 and this relay deenergizes. of the entire system which have been been employed in establishing the connection are now restored to normal condition.

Sequence switch 220 remains in position 18 until the link circuit is again seized by a register controlling mechanism when a circuit is established through the right-hand winding of relay 262, the upper contact of sequence switch spring 236 (18), the upper contact ofsequence switch spring 266 (18), the winding of relay 268, the normally closed left-hand armature contacts of relay 233, the conductor 390, the upper contact of sequence switch spring 236 (1 and 1%) and thence to ground through the resistance element 327. Relay 262 then energizes. and establishes a circuit for driving'the sequence 220 out of position 18 and into position 1, which circuit may be traced from grounded battery through the magnet winding of sequence switch 220, the lower cont-act of sequence switch spring 227 (18), the front contact and armature of relay 262, thelower contact of sequence switch spring 238 (18), and thence to ground at the lower contact of sequence switch spring 229 (18).

Restoration-0alled subscriber first to hang up.

If the called subscriber is the first to re store his receiver to its switchhook, relay 262 becomes deenergized closing a circuit for energizing relay 222, which circuit may be traced through the winding of this relay, the upper contact of sequence switch spring 223 (11 and 12), the back contact and armature of relay 262 and thence to ground at the cam springs 255. Belay 222energizes in this circuit and atits armature and front contact closes a circuit extending through the upper contact of sequence switch spring 227 (11 and 12) tor driving sequence switch 220 out oi": position-11 through position 12 and into position 13.

The circuits.

'through the right-hand winding of relay 263, the lower contact of sequence switch spring 251 (13 and 14) and through the winding of sequence switch magnet 220 for driving the sequence switch out of position 13 through position 14 and into position 15,

from which point the release of the connection proceeds in the manner prevlously described.

Called Zine busy.

If the called line was busy when its terminals were tested in position 7 of sequence switch 220, relays 234 and 232 would not have energized and consequently when sequence switch 226 arrived in position 8 and relay 222 energized, no circuit would have been. established for driving the sequence switch 220 out of position 8 and into posi' tion 10, since this circuit is open at the armature and front contact of relay 232. Since sequence switch 220 remains in position 8, a circuit is established for sending a busy tone to the line of they calling subscriber, the busy tone being associated with the secondary windings of the tone coil 272, which is at this time connected through the windings of relay 262 to the calling subscribers line, by means of the primary winding of the tone coil which is connected in a circuit extending through the upper contact of sequence switch spring 2413 (8) and thence to ground through the busy interrupter 274:.

The calling subscriber upon hearing the busy tone restores his receiver to its switchhook, thereby opening the circuit for relay 231 which deenergizes and at its armature and front contact opens the circuit of relays 207, 213 and 233 for restoring the circuits of the first line finder to normal condition, and at its armature and back contact closes a circuit for driving sequence switch 220 out of position 8 and into position 9, which circuit may be traced from grounded battery through the winding of the sequence switch magnet 220, lower contact of sequencespring 251, the right-hand winding of relay 263 and thence to ground through the front contact and armature of relay 231. In position 9 sequence switch 220 closes a circuit for relay 222, which circuit extends through the upper contact of sequence switch spring 223 (8 and 9), the back contact and armature of relay 262 and thence to ground at the lower contacts of cam 255. Relay 222 energizes and at its armature and front contact establishes a circuit through the brush carriage driving magnet 261, which circuit may be traced from grounded battery through this magnet winding, the lower contact of sequence switch spring 224: (9), the back contact and armature of relay 232 and thence to ground through the front contact and armature of relay 222. W hen the brush carriage reaches its normal position, the normal contact 269 is closed, thereby establishing a circuit extending therefrom through the. lower contact of sequence switch spring 236 (8. to 10), and through the right-hand winding of relay 262 to grounded battery, where upon relay 262 energizes opening at its armature and contact the circuit of relay 222, which in turn deenergizes opening at its armature and front contact the. circuit of the brush carriage magnet 261. Relay 262 upon energization also closes at its armature and front contact, a circuit for the holding magnet 265, which may be traced from grounded battery through winding of this magnet, the upper contact sequence switch spring 228 (9), the lower contact of sequence switch spring 227 (8 to 10), the front contact of armature 262 and thence to ground at the lower contacts of cam 255. The brush carriage is thereby brought to rest in its normal position. In parallel with the circuit of magnet 265, a. circuit is also established through the mag net of sequence switch 220 for driying the sequence switch out of position 9 and into position 10, in which position the energization of the sequence switch magnet is continued through the lower cont-act of sequence switch spring 251 (10 to 11), the right-hand winding of relay 263, and thence to ground over the back contact of relay 231 and the sequence switch continues to move into osition 12. The sequences of operations tien proceeds in the same manner as previously described in connection with the restoration of a successful connection.

F ac'lw'e of test relay s to function 1. 7207? testing the terminalaof a first finder Zinl If upon testing the terminal 230 of a first finder link which has been connected with the line of a calling subscriber, the test relays 23a and 232 fail to function properly, and relay 232 is deenergized at the time sequence switch 220 passes through position2, a circuit is established for the energization of relay 263 which circuit may be traced from grounded battery through the trip magnet winding 248, the left-hand winding of relay 263, the upper left-hand contact of sequence switch spring 247 (2), the back contact and armature of relay 232 and the front contact and armature of relay 222.- This relay energizes and closes a locking circuit for itself extending through its left-hand armature and front contact, the upper contact of sequence switch spring 229 and thence to ground as soon as sequence switch 220 reaches position 3, and at its left-hand armature and back contact opens the circuit over which relays 207, 213 and 233 are normally energized when sequence switch 220 reaches position 3. Under the influence of magnet 248, which Was energized in series with relay 263, the trip spindle rotates and at its cam contacts 255 establishes a circuit for the sequence switch magnet 220, which circuit may be traced from grounded battery through the magnet winding of sequence switch 220, the lower contact of sequence switch spring 227 (3), the front contact and armature of relay 262, this relay being energized in position 3 of the sequence switch as heretofore described, and thence to round through the contacts of cam 255.

equence switch 220 moving out of position 2 opens at the upper contact of sequence switch spring 223 the energizing circuit of relay 222, which thereupon deenergizes and at its armature and back contact provides a circuit extending through the upper contact of sequence switch spring 251 for continuing the movement of the sequence switch through positions 4 and 6 into position 8. From this point the cycle of operations continues in the manner previously described until the sequence switch is again in normal position. 7

Relay 263 remains energized until the sequence switch moves out of position 7 when the circuit for this relay is opened at the upper contact of sequence switch spring 229. At the time sequence switch 220 passed through position 2, a circuit was established for relay 325, which extends from grounded battery through the righthand winding of this relay over conductor 392, the upper contact of sequence switch spring 237, the normally closed lefthand armature contacts of relay 233, conductor 390 and thence to ground through the upper contact of sequence switch spring 326. Relay 325 energizes in this circuit and in the manner previously described causes the movement of register 130 into position 1. As soon as the sequence switch 220 leaves position 7, relay 325 dcenergizes and the circuits of the register cont-rolling mechanism are restored to normal condition with the sequence switch 320 in position 7, in which a new link circuit is associated with the register controlling mechanism to replace the link circuit which has proven defective.

Connection with a Zine in a distant exchange.

It will-now be assumed that the calling subscriber desires a connection with a line C in a distant telephone exchange. Upon the initiation of the call the subscribers line is extended in the manner previously described through the first finder switch and a second tinder switch to the register controlling mechanism, whereby sequence switch 220 of the second finder link is moved to position 3 and the register 130 is moved to position 1, as hereinbei'ore describedin connection with a local call. As soon as the dialing tone is perceived at the calling subscribers substation, the calling subscriber dials the digit 0 for obtaining a connection with the distant exchange. The register 130 thereupon follows the impulses in the manner previously described and moves through a complete revolution into its 0 position. Sequence switch 320 of the register controlling mechanism then moves from position 1 into position 2 by virtue of the circuit established at the front contact and armature of relay 343. rit this time a circuit is also established at the armature contact of relay 343, extending through the lower contact of sequence switch spring 345 (1) through the winding of relay 331 and the right-hand winding of relay 357 to grounded battery. Relay 331 does not energize in this circuit, however, since its winding is short-circuited at contact 133 (0) of register 130, the register having been set in its 0 position. Now when sequence switch 320 moves from position 1 into position 2, a circuit is established from ground at the back contact of relay 331, through the lower contact of sequence switch spring 346 (1 winding of stepping relay 355, upper contact of sequence switch spring 356 (1 to 6), conductor 393, lower contact of sequence switch spring 223 (3 to 6), and thence through the winding of relay 222 to grounded battery. Relays 355 and 222 energize in this circuit and relay 355 closes a locking circuit through its winding and the winding of relay 222 extending through the front contact and armature of relay 355 to ground for maintaining these relays energized after the initial energizing circuit is broken at the lower contact of sequence switch spring 346 as soon as sequence switch 320 reaches position 2.

Upon the energization of relay 222, a circuit is provided for the trip spindle magnet 24:8 in the manner previously described, whereupon the trip spindle starts to rotate and upon moving one step, at its upper cam springs 255 establishes a shunt circuit for the stepping relay 355. As soon as the trip spindle leaves its normal position, a circuit is closed at the lower contacts of cam 255 for driving the sequence switch 220 out of position 3 and into position 4, which circuit maybe traced :t'rom'grounded battery through the magnet winding of sequence switch 220, the lower contact of sequence.

switch spring 227 (3) ,the front contact and armature of relay 262, and thence to ground at the lower contacts of cam 255. Upon the shunting out of relay 355, this relay 'deenergizes, thereby opening the circuit extending through its winding and the winding oi relay 222, and relay 222 thereupon deenergizes, closing at its back contact and armature a circuit extending through the upper contact of sequence switch spring 251 for continuing the movement of sequence switch 220 out of position 1 and into position 8. Upon leaving position 7 sequence switch 220 opens the circuitthrough the relay 325, which thereupon deenergizes and causes the sequence switch 320 to move out of position 2 and through positions 3, 5 and 6into position 7, as has been previously described.

The calling subscribers line is new connected through the contacts of sequence switch springs 235, 237 with'the windings of the relay 231, which energizes and at its armature and front contact closes a circuit for maintaining the energization of relays 233, 213 and 207. With the brush carriage in its normal position and sequence switch 220 in position 8, a circuit is closed through the right-hand winding of relay 262, which may be traced from grounded battery through this winding, the lower contact of sequence switch spring 236 (8 to 10) and thence to ground at the normal contact 269 of the brush carriage. Relay 262 energizes in this circuit, closing a circuit for driving sequence switch 220 out of position 8, this circuit ex tending from grounded battery through the winding of sequence switch magnet 220 through the lower contact of sequence switch spring 227 (8 to 10), front contact and armature of relay-262, and thence to ground at the cam contacts 255. Upon reaching posi- 'tion 11, the circuit extending through the winding of relay 262 is opened, and this relay deenergizes establishing at its armature and back contacta circuit extending through the winding of relay 222, the upper contact of sequence switch spring 223 (11 and 12), the back contact and armature of relay 262 and thence to ground at the contacts of cam 255. Relay 222 energizes, establishing a circuit through the upper contact of sequence switchspring 227 (11 and 12), for driving the sequence switch out of position 11 and into position 13. In position 13 the circuit through the right-hand winding of relay 262 is again established for energizing this relay,

whichthereupon closes a circuit for driving sequence switch 220 out of position 13 and into position 14. In position 14 relay 222 again energizes over the circuit previously traced closing at its armature and front contact a circuit, extending through the armature and back contact of relay 232 through the lower contact of sequence switch spring 224 (14) and thence to grounded battery, through the winding of the brush carriage driving magnet 261. g

The brush carriage of the final selector r0 tat-es with its lowermost set of brushes tr-ipped, since the tripping spindle was arrested after its first step. The terminals in the first row of the switch bank are reserved for trunk lines extending between the satellite and the distant exchange, and as soon as the terminals of a free trunk line are engaged, a circuit is established from battery over the test terminal 282, through the test brush of the switch, upper contact of sequence switch spring 226 (141 and 15), the right-hand high resistance winding of test relay 23 1, the upper contact of sequence switch spring 225 (14 and 15), and thence to ground at the armature and back contact of relay 263. Test relay 23 1 upon energizing connects the winding of test relay 232 through the left-hand low resistance winding of relay 234, in parallel with its high resistance, right-hand winding, thereby reducing the potential on the test terminal 282 for making this test terminal busy. The energization of relay 232 opens at its armature and back contact, the circuit extending through the driving magnet of the brush carriage and establishes at its armature and front contact, a circuit for the holding magnet 265 which extends through the winding of this magnet, through the upper contact of sequence switch spring 228 (14s), the lower contact of sequence switch spring 227 (13 to 15), front contact and armature of relay 232, and thence to ground at front contact and armature of relay 222, and the magnet 265 upon energizing arrests the brush carriage with the brushes in engagement with the idle selected trunk. A circuit is also closed atthis time in parallel with the magnet winding 265, for driving sequence switch 220 out of position 1 1 and into position 15.

In position 15 relay 222 is deenergized, and the upper contacts of sequence switch springs 267 and 266 are closed, thereby connecting the calling subscribers line. through the conductors of the selected trunk circuit leading to the distant exchange. Upon such extension the slow-acting relay 268 energized in series with the line relay 4101 associated with the trunk circuit at the distant exchange, the relay 268 opening at its armature and back contact the circuit of relay 260 for preventing the sequence switch 220 from being driven out of position 15 until after the termination of the conversation. Upon leaving position 1 1, the circuit for relay 231 is opened at the contacts of sequence switch springs 235 and 237, but the holding ground at the armature and front contact of relay 231, which has held relays 207, 213 and 233 energized, is now replaced by ground at the upper contact of sequence switch spring 229 (15).

Upon the energization of the line relay 401 at the distant end of the trunk, the first line finder at the distant exchange is started up to seize the selected trunk in the same register 530 into position 1 in which posi" tion the dialing tone interrupter 538 is connected over register contact 535, through sequence switch contact 537 (1), to the primary winding of the dialing tone coil 524. The dialing tone is thereupon inductively transmitted through the secondary windings of this tone coil, back over the trunk circuit to the substation of the calling subscriber.- The calling subscriber upon receiving this dialing coil proceeds to dial the digits corresponding to the designation of the desired subscriber in the distant exchange. The register controlling mechanism at the distant exchange functions in the same manner as already described in connection with the setting of the register controlling mechanism at the satellite and causes the positioning of the final selector at the distant exchange, upon the terminals of the desired line. The called line is tested and if found idle is connected in a talking circuit with the calling subscriber in the same manner as described in connection with the operation of the final selector in the satellite oflice, talking current being supplied to the called subscriber through the windings of relay 462 at the distant otfice, and talking current being supplied to the calling subscriber in the satellite otfice through the windings of relay 431.

Upon the termination of a conversation the switches at the distant office are restored in the manner similar to the restoration of the switches in the satellite ofiice. VV'hen the calling subscriber restores his receiver to its switchhook, the circuit of relay 268'is opened, whereby relay 268 retracts its armature closing a circuit for the relay 260 which thereupon closes a circuit for moving sequence switch 220 out of position 15 and into position 16. In this position the trip spindle is restored to its position of rest as previously described, after which sequence switch220 is moved into position 17 and the brush carriage 261 is restored to its position of rest. Assoon as the brush carriage reaches its normal position, normal contact 269 is closed for energizing relay 262, which in the manner previously described causes the movement of sequence switch 220 into position 18 in which position the sequence switch remains until the reg ister controlling mechanism at the satellite office again seizes the link circuit for establishlng a new connection when sequence switch 220 will be driven into position 1,

talking positions, one position 13 serving local connections when relays 231'and-262 are cut into the circuit, and the other serving when the connection is established with a distant exchange.

Sequence switch 220 of the link circuit having advanced over the ringing position and the first talking position before the brushes have been moved from their normal position in search for a trunk circuit leading to the distant exchange, it is apparent that when the brushes do finally move over the trunk terminals in search of an idle trunk, that no disturbance is created at the trunk lines over which the brushes pass.

hat is claimed is:

1. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for extending connections between subscribers lines, selectorswitches in V which said link circuits terminate, a register switch controlling mechanism common to a plurality of said link circuits, and a single unitary means associated with said mechanism for selectively associating said mechanism with an idle link circuit and for controlling the sequential operation of said mechanism.

52. In a telephone exchange system, a plurality of subscribers lines, a'plurality of link circuits for extending connections between subscribers lines,.selector switches in which said link circuits terminate, a register switch: controlling mechanism common to a plurality of said link circuits, and a sequence switch associated with said mechanism for selectively associating said mechanism with an idle link circuit and for controlling the sequential operation of said mechanism;

3. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for extending connections between subscribers lines, selective "switches in which said link circuits terminate, aregister switch controlling mechanism common to a plurality of said link circuits, a sequence switch associated with 'saidmechanism for selectively associating said mechanism with an idle link'circuit, animpulse circuit" over which said mechanism is adjusted by the calling subscriberin accordance with the designation of the desired subscribers line, and a fundamental circuit over which said mechanism controls s a-id selector switches, said impulse circuit and said fundamental circuit being successively connected-with said mechanism in certain positions of said sequence switch. I 

